Flashcards for OCR 21st Century Science C5

Quick revision for C5 Chemicals in the Nautural Environment

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  • Created by: isis
  • Created on: 18-01-13 20:47
What gases are in dry air and in what percentages?
78% Nitrogen 21% Oxygen 1% Argon 0.04% Carbon Dioxide
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What is covalent bonding?
Atoms share electrons with other atoms, so that both atoms feel that they have a full outer shell.
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Name compounds that bond through covalent bonding?
Hydrogen, Carbon Dioxide and Water
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What are three different ways of representing molecules?
Molecular formula, displayed formula and 3-D models
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What is the hydrosphere?
It consists of all the water in the oceans, seas, lakes, rivers, etc AND and compounds that are dissolved in the water.
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What are most compounds in water called?
They are ionic compounds called salts.
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What are ionic compounds made from
Charged particles called ions, forming a giant lattice.
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True or False: A single crystal of salt is made from millions of ionic lattices.
False a single crystal of salt is ONE giant lattice and that is why salt crystals tend to be cuboid in shape
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Can ionic compounds conduct electrcity?
Only when dissolved in water or molten, this is because the ions are free to move.
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What colour does Sodium, Potassium, Calcium and Copper go when heated?
Sodium - Orange/yellow flame Potassium - lilac flame Calcium - brick-red flame Copper blue-green flame.
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What is is a precipitation reaction?
Where two soluble react to form an insoluble solid compound.
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Give some examples of a metal compound that precipitates out of a solution when you add an acid?
Metal Hydroxides
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How do you detect carbonates?
Add hydrochloric acid and if if it turns cloudy in limewater then carbonate ions are present.
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How do you detect sulfates?
Add dilute HCl followed by barium chloride solution (BaCl2) If a white precipitate forms then a sulfate is present.
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Why do use HCl first when trying to detect sulfates?
to get rid of any traces of carbonate ions before the test, so as not to confuse the results.
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How do you detect halides?
Add dilute nitirc acid followed by silver nitrate solutuion.
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What colour precipitate does a chloride ion give?
A white precipitate of silver chloride.
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What colour precipitate does a bromide ion give?
A cream precipitate of silver bromide
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What colour precipitate does a iodide ion give?
A yellow precipitate of silver iodide.
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What is the lithospere?
The rigig outer layer- the crust and part of the upper mantle.
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What is the lithosphere made up of?
A mixture of minerals often containg silicon, oxygen and aluminium.
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What sort of giant covalent structures can carbon form?
Diamond and graphite.
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How many covalent bonds for each carbon atom are there in diamond?
4 making it a very rigid structure.
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True of False: Diamond is the hardest substance known.
False it is the hardest NATURAL substance- it is ideal as a cutting tool.
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Describe the properties of diamonds?
It has a high melting point, does not conduct electricity as there are no free electrons and it is insoluble in water?
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What is the structure of graphite?
Each carbon atom forms 3 covalent bonds creating sheets of carbon atoms which are free to slide over each other.
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How does a pencil work?
As the layers of graphiter are held together so loosely they can be rubbed off onto paper to leave a black mark.
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Describe the characteristics of graphite?
It has a high melting point, but as there are lots of free electrons it conducts electricity.
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Name a giant covalent structure other than diamond or graphite
Silicon Dioxide
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What does Silicon dioxide (or silica) make?
Sand, each grain of sand is one giant structure of silicon and oxygen.
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How is silicon dioxide similar to diamond?
It has a similar structure so also has a high melting point and doesn't conduct electricity.
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How can we extract metals?
From ores through the process of reduction with carbon or electrolysis.
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What sort of metals can be extracted through reduction with carbon?
Metals that are less reactive than carbon.
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Why can less reactive metals be extracted through reduction?
Carbon can take the oxygen away from metals which are less reactive than itself
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How are metals that are more reactive than carbon extracted?
Electrolysis.
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What is electrolysis?
The decomposition of a substance using electricity.
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What is produced at the anode?
Non metals are produced as they are negative and are so attracted to the positive anode?
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What is produced at the cathode?
Metals are produced as they are positive and so attracted to the negative cathode.
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In electrolysis what is reduction?
the gain of electrons.
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In electrolysis what is oxidation?
The loss of electrons.
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What does PANIC stand for?
Positive Anode Negative Is Cathode.
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What does OIL-RIG stand for?
Oxidation Is Loss Reduction Is Gain
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Describe the structure of metals.
The positively charged metal ions are held together by a sea of delocalise electrons
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Wher do the free electrons in metals come from?
From the outer shell of every metal atom in the structure.
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Why are metals good conductors of heat and electricity?
The free electrons carry both heat and electrical current through the material.
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What sort of products are metals good for and explain why?
Saucepan base- heat conductivity, electrical wires- electrical conductivity, bridges and car bonnets- strength and malleability
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Why are metals strong and malleable?
They have a high tensile strength becasue the layers of atoms in a metal can slide over each other.
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Why is mining finite resources such as ores good?
Useful products can be made, it provides local people with jobs and brings money into the area, so things like transport and health can be improved
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Why is mining bad for the environment?
It uses loads of energy, scars the landscape and destroys habitats. also noise dust and pollution are caused by and increase in traffic.
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Why is recycling metals important?
It uses only a small fraction of the energy needed to mine and extract new metals. It saves money and conserves finite resources. it also cuts the amount of waste sent to landfill.
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For every 1kg of aluminium cans recycled, whaty is saved?
95% of the energy needed to mine and extract new alumikum, 4kg of aluminium ore and a lot of waste.
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Other cards in this set

Card 2

Front

What is covalent bonding?

Back

Atoms share electrons with other atoms, so that both atoms feel that they have a full outer shell.

Card 3

Front

Name compounds that bond through covalent bonding?

Back

Preview of the front of card 3

Card 4

Front

What are three different ways of representing molecules?

Back

Preview of the front of card 4

Card 5

Front

What is the hydrosphere?

Back

Preview of the front of card 5
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